-module(lrpc).
%-compile(export_all).
-export([start_server/0, server_main/0, sum/3, max/3]).

%-define(DEBUG, true).
-ifdef(DEBUG).
 -define(RETURN(ClientPid, X), 
         io:fwrite("To: ~w, Returns:~w\n", [ClientPid, X])).
-else.
 -define(RETURN(ClientPid, X), 
         ClientPid!X).
-endif.

start_server() ->
 spawn(?MODULE, server_main, []).

server_main() ->
 receive
  {call, ClientPid, FunctionId, Args} -> % 呼び出しリクエスト
   case exec(FunctionId, Args) of
    {error, Reason} -> ?RETURN(ClientPid, {return, error, Reason});
    {ok, Value} -> ?RETURN(ClientPid, {return, ok, Value})
   end;
  stop -> % プロセス終了命令
   io:fwrite("~w: bye bye.\n", [self()]),
   exit(ok);
  _Other -> io:fwrite("Oops!\n")
 end,
 server_main().

exec(sum, Args) ->
 {ok, lists:sum(Args)};
exec(max, Args) ->
 {ok, lists:max(Args)};
exec(_, _) ->
 {error, "unknown function."}.
 
%%%% クライアント側

call(ServerPid, FunctionId, Args) ->
 ServerPid! {call, self(), FunctionId, Args},
 receive
  {return, ok, Value} -> {ok, Value};
  {return, error, Reason} -> {error, Reason}
  after 2*1000 -> {error, "timeout."}
 end.
 
sum(ServerPid, N, M) -> call(ServerPid, sum, [N, M]).
max(ServerPid, N, M) -> call(ServerPid, max, [N, M]).